1
|
Vatta M, Lyons B, Heney KA, Lidster T, Merrill AR. Mapping the DNA-Binding Motif of Scabin Toxin, a Guanine Modifying Enzyme from Streptomyces scabies. Toxins (Basel) 2021; 13:toxins13010055. [PMID: 33450958 PMCID: PMC7828395 DOI: 10.3390/toxins13010055] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 12/23/2020] [Accepted: 01/09/2021] [Indexed: 11/16/2022] Open
Abstract
Scabin is a mono-ADP-ribosyltransferase toxin/enzyme and possible virulence factor produced by the agriculture pathogen, Streptomyces scabies. Recently, molecular dynamic approaches and MD simulations revealed its interaction with both NAD+ and DNA substrates. An Essential Dynamics Analysis identified a crab-claw-like mechanism, including coupled changes in the exposed motifs, and the Rβ1-RLa-NLc-STTβ2-WPN-WARTT-(QxE)ARTT sequence motif was proposed as a catalytic signature of the Pierisin family of DNA-acting toxins. A new fluorescence assay was devised to measure the kinetics for both RNA and DNA substrates. Several protein variants were prepared to probe the Scabin-NAD-DNA molecular model and to reveal the reaction mechanism for the transfer of ADP-ribose to the guanine base in the DNA substrate. The results revealed that there are several lysine and arginine residues in Scabin that are important for binding the DNA substrate; also, key residues such as Asn110 in the mechanism of ADP-ribose transfer to the guanine base were identified. The DNA-binding residues are shared with ScARP from Streptomyces coelicolor but are not conserved with Pierisin-1, suggesting that the modification of guanine bases by ADP-ribosyltransferases is divergent even in the Pierisin family.
Collapse
Affiliation(s)
- Maritza Vatta
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada;
| | - Bronwyn Lyons
- Department of Biochemistry and Molecular Biology and Center for Blood Research, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada;
| | - Kayla A. Heney
- Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada;
| | - Taylor Lidster
- Department of Biological Sciences, Brock University, St. Catherines, ON L2S 3A1, Canada;
| | - A. Rod Merrill
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada;
- Correspondence: ; Fax: +1-519-837-1802
| |
Collapse
|
2
|
The N-terminus of Paenibacillus larvae C3larvinA modulates catalytic efficiency. Biosci Rep 2021; 41:227200. [PMID: 33289829 PMCID: PMC7789906 DOI: 10.1042/bsr20203727] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 12/07/2020] [Accepted: 12/08/2020] [Indexed: 01/21/2023] Open
Abstract
C3larvinA was recently described as a mono-ADP-ribosyltransferase (mART) toxin from the enterobacterial repetitive intergenic consensus (ERIC) III genotype of the agricultural pathogen, Paenibacillus larvae. It was shown to be the full-length, functional version of the previously described C3larvintrunc toxin, due to a 33-residue extension of the N-terminus of the protein. In the present study, a series of deletions and substitutions were made to the N-terminus of C3larvinA to assess the contribution of the α1-helix to toxin structure and function. Catalytic characterization of these variants identified Asp23 and Ala31 residues as supportive to enzymatic function. A third residue, Lys36, was also found to contribute to the catalytic activity of the enzyme. Analysis of the C3larvinA homology model revealed that these three residues were participating in a series of interactions to properly orient both the Q-X-E and S-T-S motifs. Ala31 and Lys36 were found to associate with a structural network of residues previously identified in silico, whereas Asp23 forms novel interactions not previously described. At last, the membrane translocation activity into host target cells of each variant was assessed, highlighting a possible relationship between protein dipole and target cell entry.
Collapse
|
3
|
Meng YR, Zhang D, Zou X, Ma F, Kang Q, Zhang CY. A trifunctional split dumbbell probe coupled with ligation-triggered isothermal rolling circle amplification for label-free and sensitive detection of nicotinamide adenine dinucleotide. Talanta 2020; 224:121962. [PMID: 33379129 DOI: 10.1016/j.talanta.2020.121962] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 11/17/2020] [Accepted: 11/30/2020] [Indexed: 11/15/2022]
Abstract
The nicotinamide adenine dinucleotide (NAD+) is an important small biomolecule that participates in a variety of physiological functions, and it has been regarded as a potential biomarker for disease diagnosis and a promising target for disease treatment. The conventional methods for NAD+ assay often suffer from complicated procedures, expensive labeling, poor selectivity, and unsatisfactory sensitivity. Herein, we develop a label-free and sensitive method for NAD+ assay based on the integration of a trifunctional split dumbbell probe with ligation-triggered isothermal rolling circle amplification (RCA). We design a trifunctional split dumbbell probe that can act as a probe for NAD+ recognition, a template for RCA reaction, and a substrate for SYBR Green I binding. In the presence of target NAD+, it can serve as a cofactor to active E. coli DNA ligase which subsequently catalyzes the ligation of split dumbbell probe to form a circular template for RCA reaction, generating numerous dumbbell probe amplicons which can be easily and label-free monitored by using SYBR Green I as the fluorescent indicator. Due to the high fidelity of NAD+-dependent ligation and high amplification efficiency of RCA amplification, this method exhibits high sensitivity with a detection limit of 85.6 fM and good selectivity with the capability of discriminating target NAD+ from its analogs. Moreover, this method can be applied for accurate and sensitive detection of NAD+ in complex biological samples and cancer cells, holding great potential in NAD+-related biological researches and clinical diagnosis.
Collapse
Affiliation(s)
- Ya-Ru Meng
- College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Provincial Key Laboratory of Clean Production of Fine Chemicals, Shandong Normal University, Jinan, 250014, China
| | - Dandan Zhang
- College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Provincial Key Laboratory of Clean Production of Fine Chemicals, Shandong Normal University, Jinan, 250014, China
| | - Xiaoran Zou
- College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Provincial Key Laboratory of Clean Production of Fine Chemicals, Shandong Normal University, Jinan, 250014, China
| | - Fei Ma
- College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Provincial Key Laboratory of Clean Production of Fine Chemicals, Shandong Normal University, Jinan, 250014, China.
| | - Qi Kang
- College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Provincial Key Laboratory of Clean Production of Fine Chemicals, Shandong Normal University, Jinan, 250014, China.
| | - Chun-Yang Zhang
- College of Chemistry, Chemical Engineering and Materials Science, Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Key Laboratory of Molecular and Nano Probes, Ministry of Education, Shandong Provincial Key Laboratory of Clean Production of Fine Chemicals, Shandong Normal University, Jinan, 250014, China.
| |
Collapse
|
4
|
Su W, Li Z, Liu S, Ding X. Indirect Electrochemical Detection of NADH Through an Active Stainless Steel Fiber Felt (SSFF) Electrode Decorated With the Amino-Graphene/Nafion Nano Composite Films. ChemistrySelect 2018. [DOI: 10.1002/slct.201800743] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Wenqiong Su
- Institute for Personalized Medicine; School of Biomedical Engineering; Shanghai Jiao Tong University; 200240 P.R. China
| | - Zonglin Li
- Institute for Personalized Medicine; School of Biomedical Engineering; Shanghai Jiao Tong University; 200240 P.R. China
| | - Shuopeng Liu
- Institute for Personalized Medicine; School of Biomedical Engineering; Shanghai Jiao Tong University; 200240 P.R. China
| | - Xianting Ding
- Institute for Personalized Medicine; School of Biomedical Engineering; Shanghai Jiao Tong University; 200240 P.R. China
| |
Collapse
|
5
|
Lugo MR, Lyons B, Lento C, Wilson DJ, Merrill AR. Dynamics of Scabin toxin. A proposal for the binding mode of the DNA substrate. PLoS One 2018; 13:e0194425. [PMID: 29543870 PMCID: PMC5854381 DOI: 10.1371/journal.pone.0194425] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 03/04/2018] [Indexed: 12/29/2022] Open
Abstract
Scabin is a mono-ADP-ribosyltransferase enzyme and is a putative virulence factor produced by the plant pathogen, Streptomyces scabies. Previously, crystal structures of Scabin were solved in the presence and absence of substrate analogues and inhibitors. Herein, experimental (hydrogen-deuterium exchange), simulated (molecular dynamics), and theoretical (Gaussian Network Modeling) approaches were systematically applied to study the dynamics of apo-Scabin in the context of a Scabin·NAD+·DNA model. MD simulations revealed that the apo-Scabin solution conformation correlates well with the X-ray crystal structure, beyond the conformation of the exposed, mobile regions. In turn, the MD fluctuations correspond with the crystallographic B-factors, with the fluctuations derived from a Gaussian network model, and with the experimental H/D exchange rates. An Essential Dynamics Analysis identified the dynamic aspects of the toxin as a crab-claw-like mechanism of two topological domains, along with coupled deformations of exposed motifs. The “crab-claw” movement resembles the motion of C3-like toxins and emerges as a property of the central β scaffold of catalytic single domain toxins. The exposure and high mobility of the cis side motifs in the Scabin β-core suggest involvement in DNA substrate binding. A ternary Scabin·NAD+·DNA model was produced via an independent docking methodology, where the intermolecular interactions correspond to the region of high mobility identified by dynamics analyses and agree with binding and kinetic data reported for wild-type and Scabin variants. Based on data for the Pierisin-like toxin group, the sequence motif Rβ1–RLa–NLc–STTβ2–WPN–WARTT–(QxE)ARTT emerges as a catalytic signature involved in the enzymatic activity of these DNA-acting toxins. However, these results also show that Scabin possesses a unique DNA-binding motif within the Pierisin-like toxin group.
Collapse
Affiliation(s)
- Miguel R Lugo
- Department of Molecular and Cell Biology, University of Guelph, Guelph, Ontario, Canada
| | - Bronwyn Lyons
- Department of Molecular and Cell Biology, University of Guelph, Guelph, Ontario, Canada.,Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Cristina Lento
- Chemistry Department, York University, Toronto, Ontario, Canada.,The Centre for Research in Mass Spectrometry, York University, Toronto, Ontario, Canada
| | - Derek J Wilson
- Chemistry Department, York University, Toronto, Ontario, Canada.,The Centre for Research in Mass Spectrometry, York University, Toronto, Ontario, Canada
| | - A Rod Merrill
- Department of Molecular and Cell Biology, University of Guelph, Guelph, Ontario, Canada
| |
Collapse
|
6
|
Zadmard R, Akbari-Moghaddam P, Darvishi S, Mirza-Aghayan M. A highly selective fluorescent chemosensor for NADH based on calix[4]arene dimer. Tetrahedron 2017. [DOI: 10.1016/j.tet.2016.12.053] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
7
|
Lugo MR, Ravulapalli R, Dutta D, Merrill AR. Structural variability of C3larvin toxin. Intrinsic dynamics of the α/β fold of the C3-like group of mono-ADP-ribosyltransferase toxins. J Biomol Struct Dyn 2016; 34:2537-2560. [PMID: 26610041 DOI: 10.1080/07391102.2015.1123189] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
C3larvin toxin is a new member of the C3 class of the mono-ADP-ribosyltransferase toxin family. The C3 toxins are known to covalently modify small G-proteins, e.g. RhoA, impairing their function, and serving as virulence factors for an offending pathogen. A full-length X-ray structure of C3larvin (2.3 Å) revealed that the characteristic mixed α/β fold consists of a central β-core flanked by two helical regions. Topologically, the protein can be separated into N and C lobes, each formed by a β-sheet and an α-motif, and connected by exposed loops involved in the recognition, binding, and catalysis of the toxin/enzyme, i.e. the ADP-ribosylation turn-turn and phosphate-nicotinamide PN loops. Herein, we provide two new C3larvin X-ray structures and present a systematic study of the toxin dynamics by first analyzing the experimental variability of the X-ray data-set followed by contrasting those results with theoretical predictions based on Elastic Network Models (GNM and ANM). We identify residues that participate in the stability of the N-lobe, putative hinges at loop residues, and energy-favored deformation vectors compatible with conformational changes of the key loops and 3D-subdomains (N/C-lobes), among the X-ray structures. We analyze a larger ensemble of known C3bot1 conformations and conclude that the characteristic 'crab-claw' movement may be driven by the main intrinsic modes of motion. Finally, via computational simulations, we identify harmonic and anharmonic fluctuations that might define the C3larvin 'native state.' Implications for docking protocols are derived.
Collapse
Affiliation(s)
- Miguel R Lugo
- a Department of Molecular and Cell Biology , University of Guelph , Science Complex, Guelph , ON N1G2W1 , Canada
| | - Ravikiran Ravulapalli
- a Department of Molecular and Cell Biology , University of Guelph , Science Complex, Guelph , ON N1G2W1 , Canada
| | - Debajyoti Dutta
- b Faculty of Medicine, Department of Biochemistry , University of Alberta , Edmonton , AB T6G 2H7 , Canada
| | - Allan Rod Merrill
- a Department of Molecular and Cell Biology , University of Guelph , Science Complex, Guelph , ON N1G2W1 , Canada
| |
Collapse
|
8
|
Ravulapalli R, Lugo MR, Pfoh R, Visschedyk D, Poole A, Fieldhouse RJ, Pai EF, Merrill AR. Characterization of Vis Toxin, a Novel ADP-Ribosyltransferase from Vibrio splendidus. Biochemistry 2015; 54:5920-36. [PMID: 26352925 DOI: 10.1021/acs.biochem.5b00921] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Vis toxin was identified by a bioinformatics strategy as a putative virulence factor produced by Vibrio splendidus with mono-ADP-ribosyltransferase activity. Vis was purified to homogeneity as a 28 kDa single-domain enzyme and was shown to possess NAD(+)-glycohydrolase [KM(NAD(+)) = 276 ± 12 μM] activity and with an R-S-E-X-E motif; it targets arginine-related compounds [KM(agmatine) = 272 ± 18 mM]. Mass spectrometry analysis revealed that Vis labels l-arginine with ADP-ribose from the NAD(+) substrate at the amino nitrogen of the guanidinium side chain. Vis is toxic to yeast when expressed in the cytoplasm under control of the CUP1 promotor, and catalytic variants lost the ability to kill the yeast host, indicating that the toxin exerts its lethality through its enzyme activity. Several small molecule inhibitors were identified from a virtual screen, and the most potent compounds were found to inhibit the transferase activity of the enzyme with Ki values ranging from 25 to 134 μM. Inhibitor compound M6 bears the necessary attributes of a solid candidate as a lead compound for therapeutic development. Vis toxin was crystallized, and the structures of the apoenzyme (1.4 Å) and the enzyme bound with NAD(+) (1.8 Å) and with the M6 inhibitor (1.5 Å) were determined. The structures revealed that Vis represents a new subgroup within the mono-ADP-ribosyltransferase toxin family.
Collapse
Affiliation(s)
- Ravikiran Ravulapalli
- Department of Molecular and Cellular Biology, University of Guelph , Guelph, Ontario, Canada N1G 2W1
| | - Miguel R Lugo
- Department of Molecular and Cellular Biology, University of Guelph , Guelph, Ontario, Canada N1G 2W1
| | - Roland Pfoh
- Department of Biology, York University , Toronto, ON, Canada M3J 1P3.,Department of Biochemistry, University of Toronto , Toronto, ON, Canada M5S 1A8.,Campbell Family Institute for Cancer Research, Princess Margaret Hospital , Toronto, ON, Canada M5G 1L7
| | - Danielle Visschedyk
- Department of Molecular and Cellular Biology, University of Guelph , Guelph, Ontario, Canada N1G 2W1
| | - Amanda Poole
- Department of Molecular and Cellular Biology, University of Guelph , Guelph, Ontario, Canada N1G 2W1
| | - Robert J Fieldhouse
- Computational Biology Center, Memorial Sloan-Kettering Cancer Center , New York, New York 10065, United States.,Department of Systems Biology, Harvard Medical School , Boston, Massachusetts 02115, United States
| | - Emil F Pai
- Department of Biochemistry, University of Toronto , Toronto, ON, Canada M5S 1A8.,Campbell Family Institute for Cancer Research, Princess Margaret Hospital , Toronto, ON, Canada M5G 1L7.,Departments of Medical Biophysics and Molecular Genetics, University of Toronto , Toronto, ON, Canada M5S 1A8
| | - A Rod Merrill
- Department of Molecular and Cellular Biology, University of Guelph , Guelph, Ontario, Canada N1G 2W1
| |
Collapse
|
9
|
Li Z, Su W, Liu S, Ding X. An electrochemical biosensor based on DNA tetrahedron/graphene composite film for highly sensitive detection of NADH. Biosens Bioelectron 2015; 69:287-93. [PMID: 25770460 DOI: 10.1016/j.bios.2015.02.031] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 02/07/2015] [Accepted: 02/19/2015] [Indexed: 12/15/2022]
Abstract
Dihydronicotinamide adenine dinucleotide (NADH) is a major biomarker correlated with lethal diseases such as cancers and bacterial infection. Herein, we report a graphene-DNA tetrahedron-gold nanoparticle modified gold disk electrode for highly sensitive NADH detection. By assembling the DNA tetrahedron/graphene composite film on the gold disk electrode surface which prior harnessed electrochemical deposition of gold nanoparticles to enhance the effective surface area, the oxidation potential of NADH was substantially decreased to 0.28V (vs. Ag/AgCl) and surface fouling effects were successfully eliminated. Furthermore, the lower detection limit of NADH by the presented platform was reduced down to 1fM, with an upper limit of 10pM. Both the regeneration and selectivity of composite film-modified electrode are investigated and proved to be robust. The novel sensor developed here could serve as a highly sensitive probe for NADH detection, which would further benefit the field of NADH related disease diagnostics.
Collapse
Affiliation(s)
- Zonglin Li
- Med-x Research Institute, Shanghai Jiao Tong University, Shanghai 200240, PR China
| | - Wenqiong Su
- School of Chemistry and Chemical Engineering, State Key Laboratory Metal Matrix Composities, Shanghai Jiao Tong University, Shanghai, 200240, PR China
| | - Shuopeng Liu
- Med-x Research Institute, Shanghai Jiao Tong University, Shanghai 200240, PR China
| | - Xianting Ding
- Med-x Research Institute, Shanghai Jiao Tong University, Shanghai 200240, PR China.
| |
Collapse
|
10
|
Krska D, Ravulapalli R, Fieldhouse RJ, Lugo MR, Merrill AR. C3larvin toxin, an ADP-ribosyltransferase from Paenibacillus larvae. J Biol Chem 2014; 290:1639-53. [PMID: 25477523 DOI: 10.1074/jbc.m114.589846] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
C3larvin toxin was identified by a bioinformatic strategy as a putative mono-ADP-ribosyltransferase and a possible virulence factor from Paenibacillus larvae, which is the causative agent of American Foulbrood in honey bees. C3larvin targets RhoA as a substrate for its transferase reaction, and kinetics for both the NAD(+) (Km = 34 ± 12 μm) and RhoA (Km = 17 ± 3 μm) substrates were characterized for this enzyme from the mono-ADP-ribosyltransferase C3 toxin subgroup. C3larvin is toxic to yeast when expressed in the cytoplasm, and catalytic variants of the enzyme lost the ability to kill the yeast host, indicating that the toxin exerts its lethality through its enzyme activity. A small molecule inhibitor of C3larvin enzymatic activity was discovered called M3 (Ki = 11 ± 2 μm), and to our knowledge, is the first inhibitor of transferase activity of the C3 toxin family. C3larvin was crystallized, and its crystal structure (apoenzyme) was solved to 2.3 Å resolution. C3larvin was also shown to have a different mechanism of cell entry from other C3 toxins.
Collapse
Affiliation(s)
- Daniel Krska
- From the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Ravikiran Ravulapalli
- From the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Robert J Fieldhouse
- the Computational Biology Center, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, and the Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115
| | - Miguel R Lugo
- From the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - A Rod Merrill
- From the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada,
| |
Collapse
|
11
|
Zhang Y, Liu S, Lajoie G, Merrill AR. The role of the diphthamide-containing loop within eukaryotic elongation factor 2 in ADP-ribosylation by Pseudomonas aeruginosa exotoxin A. Biochem J 2008; 413:163-74. [PMID: 18373493 DOI: 10.1042/bj20071083] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
eEF2 (eukaryotic elongation factor 2) contains a post-translationally modified histidine residue, known as diphthamide, which is the specific ADP-ribosylation target of diphtheria toxin, cholix toxin and Pseudomonas aeruginosa exotoxin A. Site-directed mutagenesis was conducted on residues within the diphthamide-containing loop (Leu693-Gly703) of eEF2 by replacement with alanine. The purified yeast eEF2 mutant proteins were then investigated to determine the role of this loop region in ADP-ribose acceptor activity of elongation factor 2 as catalysed by exotoxin A. A number of single alanine substitutions in the diphthamide-containing loop caused a significant reduction in the eEF2 ADP-ribose acceptor activities, including two strictly conserved residues, His694 and Asp696. Analysis by MS revealed that all of these mutant proteins lacked the 2'-modification on the His699 residue and that eEF2 is acetylated at Lys509. Furthermore, it was revealed that the imidazole ring of Diph699 (diphthamide at position 699) still functions as an ADP-ribose acceptor (albeit poorly), even without the diphthamide modification on the His699. Therefore, this diphthamide-containing loop plays an important role in the ADP-ribosylation of eEF2 catalysed by toxin and also for modification of His699 by the endogenous diphthamide modification machinery.
Collapse
Affiliation(s)
- Yong Zhang
- Department of Molecular and Cellular Biology, Biophysics Interdepartmental Group, University of Guelph, Guelph, ON, Canada
| | | | | | | |
Collapse
|
12
|
Lemire J, Mailloux RJ, Appanna VD. Mitochondrial lactate dehydrogenase is involved in oxidative-energy metabolism in human astrocytoma cells (CCF-STTG1). PLoS One 2008; 3:e1550. [PMID: 18253497 PMCID: PMC2212712 DOI: 10.1371/journal.pone.0001550] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2007] [Accepted: 01/14/2008] [Indexed: 11/24/2022] Open
Abstract
Lactate has long been regarded as an end product of anaerobic energy production and its fate in cerebral metabolism has not been precisely delineated. In this report, we demonstrate, for the first time, the ability of a human astrocytic cell line (CCF-STTG1) to consume lactate and to generate ATP via oxidative phosphorylation. (13)C-NMR and HPLC analyses aided in the identification of tricarboxylic acid (TCA) cyle metabolites and ATP in the astrocytic mitochondria incubated with lactate. Oxamate, an inhibitor of lactate dehydrogenase (LDH), abolished mitochondrial lactate consumption. Electrophoretic and fluorescence microscopic analyses helped localize LDH in the mitochondria. Taken together, this study implicates lactate as an important contributor to ATP metabolism in the brain, a finding that may significantly change our notion of how this important organ manipulates its energy budget.
Collapse
Affiliation(s)
- Joseph Lemire
- Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, Canada
| | - Ryan J. Mailloux
- Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, Canada
| | - Vasu D. Appanna
- Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario, Canada
| |
Collapse
|
13
|
Singh R, Mailloux RJ, Puiseux-Dao S, Appanna VD. Oxidative stress evokes a metabolic adaptation that favors increased NADPH synthesis and decreased NADH production in Pseudomonas fluorescens. J Bacteriol 2007; 189:6665-75. [PMID: 17573472 PMCID: PMC2045160 DOI: 10.1128/jb.00555-07] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The fate of all aerobic organisms is dependent on the varying intracellular concentrations of NADH and NADPH. The former is the primary ingredient that fuels ATP production via oxidative phosphorylation, while the latter helps maintain the reductive environment necessary for this process and other cellular activities. In this study we demonstrate a metabolic network promoting NADPH production and limiting NADH synthesis as a consequence of an oxidative insult. The activity and expression of glucose-6-phosphate dehydrogenase, malic enzyme, and NADP(+)-isocitrate dehydrogenase, the main generators of NADPH, were markedly increased during oxidative challenge. On the other hand, numerous tricarboxylic acid cycle enzymes that supply the bulk of intracellular NADH were significantly downregulated. These metabolic pathways were further modulated by NAD(+) kinase (NADK) and NADP(+) phosphatase (NADPase), enzymes known to regulate the levels of NAD(+) and NADP(+). While in menadione-challenged cells, the former enzyme was upregulated, the phosphatase activity was markedly increased in control cells. Thus, NADK and NADPase play a pivotal role in controlling the cross talk between metabolic networks that produce NADH and NADPH and are integral components of the mechanism involved in fending off oxidative stress.
Collapse
Affiliation(s)
- Ranji Singh
- Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario P3E 2C6, Canada
| | | | | | | |
Collapse
|
14
|
Kim C, Slavinskaya Z, Merrill A, Kaufmann S. Human alpha-defensins neutralize toxins of the mono-ADP-ribosyltransferase family. Biochem J 2006; 399:225-9. [PMID: 16817779 PMCID: PMC1609915 DOI: 10.1042/bj20060425] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Various bacterial pathogens secrete toxins, which are not only responsible for fatal pathogenesis of disease, but also facilitate evasion of host defences. One of the best-known bacterial toxin groups is the mono-ADP-ribosyltransferase family. In the present study, we demonstrate that human neutrophil alpha-defensins are potent inhibitors of the bacterial enzymes, particularly against DT (diphtheria toxin) and ETA (Pseudomonas exotoxin A). HNP1 (human neutrophil protein 1) inhibited DT- or ETA-mediated ADP-ribosylation of eEF2 (eukaryotic elongation factor 2) and protected HeLa cells against DT- or ETA-induced cell death. Kinetic analysis revealed that inhibition of DT and ETA by HNP1 was competitive with respect to eEF2 and uncompetitive against NAD+ substrates. Our results reveal that toxin neutralization represents a novel biological function of HNPs in host defence.
Collapse
Affiliation(s)
- Chun Kim
- *Department of Immunology, Max Planck Institute for Infection Biology, Schumannstrasse 21-22, D-10117 Berlin, Germany
| | - Zoya Slavinskaya
- †Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - A. Rod Merrill
- †Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Stefan H. E. Kaufmann
- *Department of Immunology, Max Planck Institute for Infection Biology, Schumannstrasse 21-22, D-10117 Berlin, Germany
- To whom correspondence should be addressed (email )
| |
Collapse
|
15
|
Yates SP, Jørgensen R, Andersen GR, Merrill AR. Stealth and mimicry by deadly bacterial toxins. Trends Biochem Sci 2006; 31:123-33. [PMID: 16406634 DOI: 10.1016/j.tibs.2005.12.007] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2005] [Revised: 11/21/2005] [Accepted: 12/21/2005] [Indexed: 11/19/2022]
Abstract
Diphtheria toxin and exotoxin A are well-characterized members of the ADP-ribosyltransferase toxin family that function as virulence factors in the pathogenic bacteria Corynebacterium diphtheriae and Pseudomonas aeruginosa. Recent high-resolution structural data of the Michaelis (enzyme-substrate) complex of the P. aeruginosa toxin with an NAD(+) analog and eukaryotic elongation factor 2 (eEF2) have provided insights into the mechanism of inactivation of protein synthesis caused by these protein factors. In addition, rigorous steady-state and stopped-flow kinetic analyses of the toxin-catalyzed reaction, in combination with inhibitor studies, have resulted in a quantum leap in our understanding of the mechanistic details of this deadly enzyme mechanism. It is now apparent that these toxins use stealth and molecular mimicry in unleashing their toxic strategy in the infected host eukaryotic cell.
Collapse
Affiliation(s)
- Susan P Yates
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | | | | | | |
Collapse
|
16
|
Jørgensen R, Merrill AR, Yates SP, Marquez VE, Schwan AL, Boesen T, Andersen GR. Exotoxin A-eEF2 complex structure indicates ADP ribosylation by ribosome mimicry. Nature 2005; 436:979-84. [PMID: 16107839 DOI: 10.1038/nature03871] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2005] [Accepted: 06/03/2005] [Indexed: 11/09/2022]
Abstract
The bacteria causing diphtheria, whooping cough, cholera and other diseases secrete mono-ADP-ribosylating toxins that modify intracellular proteins. Here, we describe four structures of a catalytically active complex between a fragment of Pseudomonas aeruginosa exotoxin A (ETA) and its protein substrate, translation elongation factor 2 (eEF2). The target residue in eEF2, diphthamide (a modified histidine), spans across a cleft and faces the two phosphates and a ribose of the non-hydrolysable NAD+ analogue, betaTAD. This suggests that the diphthamide is involved in triggering NAD+ cleavage and interacting with the proposed oxacarbenium intermediate during the nucleophilic substitution reaction, explaining the requirement of diphthamide for ADP ribosylation. Diphtheria toxin may recognize eEF2 in a manner similar to ETA. Notably, the toxin-bound betaTAD phosphates mimic the phosphate backbone of two nucleotides in a conformational switch of 18S rRNA, thereby achieving universal recognition of eEF2 by ETA.
Collapse
Affiliation(s)
- René Jørgensen
- Centre for Structural Biology, Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10C, DK-8000, Denmark
| | | | | | | | | | | | | |
Collapse
|